The invention relates to an apparatus for treating blood in an extracorporeal circuit, in particular a hemodialysis apparatus and a hemofiltration apparatus, either of which have an element which is divided by a membrane into two chambers apparatus according to the preamble of claim 1 and a hemofiltration apparatus according to the preamble of claim 2.
A hemodialysis apparatus comprises an exchange element, in particular a dialyzer, which is divided by a membrane into two chambers, the first chamber being connected into a dialysis solution and the second chamber being connected into a blood path, the dialysis solution path comprising a dialysis solution source having at least one concentrate admission, a fresh water source and a temperature control unit and the blood path comprising at least one blood pump and a drip chamber downstream of the dialyzer.
A hemofiltration apparatus comprises a hemofilter which is also divided by a membrane into two chambers, the first chamber serving to receive hemofiltrate, charged with metabolism products, from blood and the second chamber likewise being connected into a blood path. The hemofiltrate amount removed is replaced approximately by an equal amount of substitution solution (minus the amount to be ultrafiltered) which is added to the blood downstream of the exchange element at a predetermined temperature.
The purpose of blood purification apparatuses used in dialysis or hemofiltration is of course to replace non-functioning kidneys in cases of acute or chronic uremia. Although these apparatuses are still not yet perfect it has been possible in the course of time to develop the method so that a large number of chronically uremic patients can survive with satisfactory life quality.
To replace at least the functions necessary for maintaining life, the blood must be freed from uremic toxins, the electrolyte metabolism and the acid-base balance maintained and part of the fluid amount absorbed through foodstuff and beverages removed.
This is mainly done with the method of hemodialysis in which blood in an extracorporeal circuit is led past a semipermeable membrane, past the other side of which a dialysis solution is conducted whose electrolyte composition is substantially equal to that of the blood. When this is done the uremic toxins pass from the blood into the dialysis solution and an equalization of the concentrations results. If a pressure difference is established between the blood and the dialysis solution a passage of fluid will also take place, i.e. of ultrafiltrate, and thus the desired fluid withdrawal. Due to the semipermeable properties of the membrane the vital blood corpuscles and proteins are retained in the blood.
In another known method, that is hemofiltration, blood is conducted in an extracorporeal circuit through a hemofilter by which an ultrafiltrate is withdrawn containing the uremic toxins. At the same time, in a first nutrient an equal quantity of a uremic-toxin-free substitution solution is again added in proportion to the blood. In the exchange element used in this method, which may be a dialyzer or a hemofilter, an exchange thus takes place of fluid components to another fluid or a fluid flows along another fluid, for example blood plasma along dialysis solution. Since these fluids or solutions have different temperatures a temperature or heat exchange also takes place.
In DE-OS 3,313,421 such hemodialysis and hemofiltration apparatuses are described. In these known apparatuses the dialysis solution source or substituate source is heated to a predetermined temperature with a temperature regulating unit, the temperature of the source being passed from a temperature detector to a control unit which controls the heating means in accordance with said measured temperature value and a predetermined temperature value. The predetermined temperature value is entered by the attending physician prior to the dialysis session and thereafter kept constant during the entire treatment.
In an article by Q. Maggiore et al. in Proc. EDTA (1981) Vol. 18, p. 597-602, it is shown that the frequently observed and to this date generally accepted better blood pressure stability in the method of insulated ultrafiltration is due to the fact that in this method thermal energy is withdrawn from the blood of the patient. In particular, it has been found that during conventional hemodialysis as well a better blood pressure stability is achieved if the temperature of the dialysis solution is lowered from the usual value of 37.degree. C. to 34.degree. C. It was however also observed that many patients found this temperature drop unpleasant.
By this step the blood temperature in the arterial tubing system was kept substantially constant. The measuring means used were thermistors inserted directly into the tubing system. Consequently, the entire system had to be subsequently sterilized.
In a later article by Q. Maggiore et al. in Trans Am Soc Artif Intern Organs (1982), Vol. 28, p. 523-527, it is shown that in hemofiltration as well the thermal energy balance influences the circulation stability. Measurements were made from which it is apparent that in conventional hemodialysis energy is supplied to the extracorporeal circuit. This is considered to be a cause for the rise of the body temperature which has a disadvantageous effect on the condition of the patient. As measuring means in the extracorporeal circuit special plastic disposable articles were used which permitted introduction of a thermometer without direct blood contact. A constant measurement deviation of 1.degree. C. occurs.
Whereas K. Schafer et al. in The International Journal of Artificial Organs (1983), Vol. 6, p. 75-76, doubts any influence of the blood temperature and thus the thermal energy balance on the circulation stability, T. Kishimoto et al. in Dialysis & Transplantation (1986) Vol 15., No. 6, p. 329-333, confirmed the opinions of Q. Maggiore in so far as they referred to hemodialysis.
As is known, as a rule a loss of energy occurs on the reflux side in hemodialysis and on the influx and reflux sides in the extracorporeal blood circuit in hemofiltration.
The fixedly entered lowering of the temperature of the dialysis solution is frequently not enough to effect temperature balance. This is due to the reaction of the individual patients to the particular dialysis conditions. Thus, in this respect it is not possible to ensure with the known temperature lowering that the patient is adequately temperature-compensated, i.e. a feverish reaction nevertheless frequently occurs and leads to a reduction of the peripheral resistance of the patient and thus to a considerable strain.
The problem underlying the invention is to further develop the apparatus of the type mentioned at the beginning so that the energy balance of a patient subjected to hemodialysis or hemofiltration is improved.